This invention relates to a pulley pinch force control device for an infinitely variable transmission installed in an automotive vehicle.
Conventionally, a pulley pinch force control device for an infinitely variable transmission has been proposed, e.g by U.S. Pat. No. 4,152,947, which comprises a cylinder affixed to a shaft of a primary pulley and cooperating with a movable conical disc to define therebetween a cylinder space to be supplied with a hydraulic fluid for urgingly displace the movable conical disc relative to an immovable conical disc, an annular groove formed in an outer peripheral portion of the cylinder, a Pitot tube for measuring the fluid pressure in the annular groove which is dependent upon the speed of the primary pulley, and a control valve for controlling the pinch force of a secondary pulley in response to the fluid pressure measured by the Pitot tube.
However, the pulley pinch force control device of this type requires the provision of an annular groove, a Pitot tube, a control valve, etc., causing disadvantages such as complication in structure and pipe arrangement, and difficulty in laying out such component parts and their related parts.